The present invention relates to improvements in an ion source particularly for use in an ion microanalyzer.
An ion microanalyzer is an apparatus for obtaining a magnified image of the surface of the specimen on the screen of a cathode ray tube (CRT). A primary ion beam is generated in an ion source and is scanned over the surface of the specimen. The incident beam causes secondary ions to be emitted from the specimen surface. The secondary ions are detected and the detection signal is used to modulate the intensity of the electron beam in the CRT. Of course, the primary ion beam is scanned over the specimen in synchronism with the scanning of the electron beam in the CRT. A background discussion of certain ion microprobes is set forth in McGraw-Hill Yearbook of Science and Technology 1973 (McGraw-Hill 1974).
Generally, for obtaining a clear image of the specimen surface, it is necessary to increase the brightness (intensity) of an ion source as much as possible. Further, a cesium Cs+ ion beam or another alkali metal ion beam as a primary ion beam is required for certain observation purposes. However, operation of conventional ion sources for generating alkali metal ion beam is very troublesome. Almost all of these conventional ion sources use a sample of the alkali metal which is a substance which reacts furiously in the atmosphere.